Decimal separators and thousands separators – commas or dots?

To summarise the current standards:

Decimal separator:

–          English (as well as most Asian languages) uses a decimal dot, and a comma to separate thousands

–          All other European languages use a decimal comma, (with a couple of exceptions such as Mexican Spanish)

–          ISO allows both, but in the long term is encouraging the standardisation of the dot (they used to encourage the comma, but calculators and computers have accustomed people to the dot)

–          SI (i.e. the official metric system) follows ISO

Thousands separator:

–          English uses the comma to separate thousands and millions

–          The other European languages mostly use a dot

–          Some, like French, use a thin space instead

–          ISO encourages the use of a thin space, partly to avoid the confusion between dot and comma


My favourite bit of confusion is the billion, which in English (and Portuguese Brazilian) is one thousand million (10 to the power 9), whereas everything else in the world it is one million million (10 to the power 12, the same as the English trillion). A number of languages have the “milliard”, which is the same as the English billion. So you end up with these wonderful equivalences:


EN                          Europe

1.234 million =  1,234 million (10 to the 6)

1.234 billion =    1.234 million (10 to the 9)

1,234 billion =    1,234 billion (10 to the 12)